C900 coil failing?

Question

1987 C900 T16S (Aero, SPG etc)Suffering what I can only describe as a misfire under power at high revs. (>3000rpm)  The engine note changes and power holds back.Elsewhere wiser men than I have pointed me towards the coil.I carried out the test in the Bentley manual today.I get 1.1 ohms across the outer terminals where the manual suggests 0.5 to 0.9 ohms is the correct rangeI get 8290 ohms across -ve terminal to centre tower when Bentley suggests 7000-8000 ohms.Should I be replacing the coil?  I'm fairly happy my meter is working properly.  Is this far enough out of spec, or should I continue looking for another fault?CheersAlParking sensors?  On a Micra?  Wouldn't it be quicker to open the door and feel round the back?

Saab C900 Viggenist · Accepted Answer

Suspect the ignition leads, distributor cap and roter before the coil - the leads and in the distributor cap are where the high voltage flows are occuring and that's where things will degrade fastest. Coils are made to tolerate very extreme ranges of temperature, even the generic Bosch ones, along with all the electrical stresses.

Also check the spark plugs. Make sure they're the correct type, and that they're gapped to the right distance (0.6 to 0.7 mm).

Craig.

pjgh93 · Answer

Have you checked the distributor advance capsule, yet?Dunno about the coil ... for the price, replace it?

Marty · Answer

In a turbo, this is a classic sign of the spark plug gap being too wide. Under boost the extra compression prevents spark from jumping the gap properly. Pull the plugs and re-gap them to spec or replace them.

C900 coil failing?

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